My Valves and Pistons - Feedback Please

I have some pictures of the valves and pistons that I'd appreciate some feedback on. This fall, before putting the bike away, I had some cold starting issues in that it would start fine on the choke but then quickly die if I never kept giving it a bit of gas. Turns out one cylinder wasn't firing. It was mostly #2, but when I took the carbs apart for cleaning (multiple times) it used to mysteriously switch to #1. If I changed or cleaned anything it would sometimes go back to #2. The majority though it would be #2 not firing. When I turned off the choke you could then hear backfiring as the dead cylinder kicked in. Once warm everything ran fine. Also, I checked the valve clearances and exhaust were all in spec, but all the intakes were out of spec, with #1 being the worst. I couldn't get my smallest feeler gauge under.

So this winter I decided to take the head off, to have a look, clean everything, replace seals and reshim.

Please keep these issues in mind when looking at the pics.

This is my first time taking any kind of engine apart and so I wasn't sure what to expect. I thought everything would be black but in mine there is a lot of real flaky carbon, which I wasn't expecting. Is this an indication of anything? Also, the valves on #3 and #4 were by far the flakiest, which I definitely wasn't expecting since these cylinders always seem to be running fine.

Also, as you'll see the #1 exhaust valve is a different colour than the others. Is this the colour they should all be, or is this one looking more burnt?

Sorry for being long winded Smile Thanks for listening.

All the valves:

#1 and #2 Valves (tan one is the #1 exhaust):

#3 and #4 Valves (notice the flakiness):

#2 Piston:

#3 Piston:

#4 Piston (#1 looks almost identical):

Hey Deac....

What do your spark plugs look like?
Notice any differences between each cylinder....

"all the intakes were out of spec, with #1 being the worst. I couldn't get my smallest feeler gauge under"...

Hmmm..... Unfortunately I don't know the KZ 650 specs but for the KZ 900 .05 to .10mm is the specification where all intakes and exhaust should be close to the same...

Based on recommendations from Larry C, w/new shims set mine at .04-.07mm spec... Mine came out at .05 for all valves.

Are your intakes fully seated or is it they just have the wrong size shims installed....?

The there's the question that is asked a thousand time... What's the compression measurements you obtained?

Does the exhaust smoke excessively? If so, which color, white, black or brown...

After warming up, does it run significantly differently (better or worse) in cold versus hot weather.

Could be just carb cleaning and adjustments.

OMR

#1/2 appear less affected by whatever's causing carbon buildup in #3/4 relating imo to compression, spark quality, and/or mixture.

Are pre-teardown figures available for compression, valve clearances, leakdown test, visual spark quality?

Would again clean #3/4 carb pilot circuits (air and fuel passages and assure undamaged correct size pilot jets). If not already done, would install brand new pilot jets, as they could have suffered virtually imperceptible damage by repetitive agressive cleanings. And assure float levels aren't too high (clear tube test also works with carbs sitting level on workbench).

If using pods, assure breathing freely (not dirty, over-oiled or otherwise clogged, damaged or waterlogged.)

Looks like head gasket was sealing just fine. May end up concluding that head removal in this instance served mostly as a good educational exercise.

Good Luck!

P.S. Are you bucking for extra credit in timebomb's class? :laugh:

OMR, my spark plugs look fine to me, maybe a bit on the blacker side, but not too bad. With that said, when having the dead cylinder issue the offending plug would be a bit wet, but after it gets running it is fine. Also, the valve appear to be seating fine, but right now I have the cam off so hard to tell. I'm going to clean them all up, and hopefully lap them while I'm at it.

The exhaust has a bit of smoke on startup/choke, it's a bit whitish/blueish. When warm it's fine. I'm replacing the valve seals while I'm at as I'm thinking they may be causing the bit of smoke. Regardless, I'll change them anyway, since I only got this bike last year and have no idea of the history. May as well do it now while I have it opened, so I don't need to open it up again.

Once warm it runs great (with the exception of a flat spot between 5-7k), regardless of the outside temps.

Patton, my compression numbers look fine to me:

Dry:
#1 - 160
#2 - 160
#3 - 165
#4 - 170

Wet:
#1 - 170
#2 - 170
#3 - 170
#4 - 170

The valve clearances prior to tear down were (sorry never had a metric gauge):

Exhaust:
#1 - 0.005" or 0.127mm
#2 - 0.004" or 0.102mm
#3 - 0.004" or 0.102mm
#4 - 0.006" or 0.152mm

Intake:
#5 - <0.002" or <0.051mm (0.002 was the smallest gauge I had)
#6 - 0.0025" or 0.0647mm
#7 - 0.0025" or 0.0647mm
#8 - 0.002" or 0.051mm

I haven't done a leakdown. Carb float levels were set while I was having these issues, but I'll be checking them again in the spring.

I'll be picking up new jets, valve seals, and Dyna ignition and coils this winter, so hopefully these help.

So is the over-black flakes a sign of overly rich state? Also, what about the #1 exhaust being a different colour, is this anything to be concerned?

Thanks

Patton, as for being in timebomb's class, I'm not even qualified to clean his chaulkboard

While your having your seals replace, best to replace the guides as well....

Black plugs... running a little rich seems to be the first thought to mind.

Not sure what plugs are recommended for your 650 or if you have the manual on your bike but here's what the KZ900 manuals depicts regarding the spark plug conditions and selection of spark plugs used (Hot/Cold plugs)....

OMR

I used to have the exact same problem on my 76 900. After multiple investigations it wound up being the choke plungers. They did not seat correctly inside the carburetor. even now this happens every once in a while and I have to "POP the chokes up and down a couple of times to seat them shut. I guarantee you 90% sure that it is a carb problem. Make sure that you pull every jet and every adjustment screw. I wash everything out with ZEP Orange cleaner by soaking everything. Than blow threw every hole and make sure that the amount of air in one carb is the same as in every other when blowing threw the holes. Check all the seats in the jet openings so nothing leaks when you put things back together. Inspect the Fuel enrichning (choke) plungers so the rubber seats are not cracked or dimpled. also check the seats they sit on.

What brand of gas are you using? Octane? Does anyone use a fuel additive?

Looks like one of those spark plugs in the pictures above, isn't in the chamber completely.

NGK's website has great techical infomation on spark plugs:
www.ngksparkplugs.com/tech_support/spark...s/index.asp?mode=nml
Read up on the heat range information, and other FAQ's on their site as well.
www.ngksparkplugs.com/tech_support/spark...s/index.asp?mode=nml

Cold starting issues usually indicates a lean condition, and hot starting issues usually indicates a rich condition.

Good luck on your rebuild. Fun ain't it?